This invention relates in general to a composition for controlling ectoparasites. More particularly this invention relates to such a composition employing a pyrethroid in concentrations greater than 50% by weight of the total composition.
Ectoparasidic arthropods such as ticks, flies and fleas are often found on mammals, such as humans and a variety of animals. Ectoparasites will feed off their mammal host and are a constant source of irritation to the host. It is therefore desirable to control such infestations. By control, it is meant that, desirably, about 80% by weight of all parasites on the host are killed or repelled. Control of tick infestation on all mammals, especially household pets, has recently assumed greater importance than at an other recent time because of the discovery that certain tick species may carry the micro-organism responsible for the transmission of Lyme disease to humans.
While there are known compositions and methods for controlling ectoparasites, many of them are systemic products. That is, they are products containing active parasiticides that enter the bloodstream of the host in order to create the insecticidal effect. Systemic insecticides are generally less desirable if suitable alternatives exist. Because systemic products, even if topically applied, must enter into the host bloodstream, they are more likely to be toxic to the host. In addition, systemic products that are not applied topically can be difficult to administer. They may require injection equipment or involve the difficult task of getting an animal to swallow oral formulations.
Liquid compositions containing up to 50% by weight of a pyrethroid are known as are methods for applying said formulations topically. See for example, U.K. Pat. 2,088,212 to Kieran & Townsend. However, known compositions do not encompass the formulation of liquid compositions containing pyrethroid in an amount greater than 50% by weight of the total composition, like those of the instant invention. It is surprising that such concentrated formulations do not cause irritation and toxicity. It would be anticipated that highly concentrated solutions of a pyrethroid, when applied to the skin, would be absorbed into the host and result in systemic toxicity, or would cause severe skin irritation. The present invention encompasses a topical formulation of greater than 50% by weight of a pyrethroid that is non-irritating and non-toxic to the host animal. The present invention also encompasses a method of controlling ectoparasites wherein the total formulation can be applied as a small dose to one or more localized regions on the skin of the hosts. The concentrated formulation applied in this manner spreads over relatively all of the body surface of the host and effectively controls ectoparasites.
Although applicant does not wish to be bound by theory or speculation, it is believed that one reason why the prior art does not teach the use of such highly concentrated pyrethroid formulations is because of the solvent systems heretofore employed. For example, U.K. Patent No. 2,088,212 teaches the dissolution of solid pyrethroids into liquid formulations by using undesirable, irritating, organic solvents such as xylene, toluene, and cyclohexanone. It teaches the use of one of these solvents in conjunction with alkyl glycol ethers. It also teaches the use of combinations of the three organic solvents in conjunction with a glycol. The referenced U.K. patent does not teach the use of glycols without adding other undesirable and irritating components. Those skilled in the art would not expect that the weak solvent power of the glycols could be compatible with commercial production methods. When the active ingredients according to the present invention are formulated in an alkyl glycol ether solvent, the resulting liquid formulation can then be used as an ingredient in formulating other topical compositions.
Concentrations of more than 50% by weight make topical application of the composition more convenient and more aesthetic than ever before. The higher the concentration, the smaller the dose for effective ectoparasite control. A small dose can be applied to a relatively small region of the skin, thus preventing the host from being covered with solvent. This formula and method of application is particularly useful for treating domestic animals, because the animal will not drip solvent or feel sticky when petting immediately after application. Such small doses can be applied without the treated animal being made aware thus easing administration. Although the composition is applied as one or more small doses to a localized region on the animal, the pyrethroid translocates to effectively control ectoparasite infestation over relatively all of the animal. Formulations containing more than 50% by weight of a pyrethroid thus obtain many advantages not taught by the prior art of using formulations with maximum concentrations of up to 50% by weight of the total formulation.
Topical compositions can be formulated to take a variety of physical states. They can be a mixture of liquids or a solid active agent can be dissolved in solution. Alternatively, the active agent may be carried in a suspension or emulsion, or may be as a microencapsulation and carried in a suspension. The suspensions can be water or oil based sols, gels, or ointments. Emulsion carriers contain both aqueous and oily components and can take the form of creams, lotions, or ointments. or ointments.
In addition, topical administration is further made convenient if the active agent insecticide is contained in an optimal composition. An optimal composition has the following characteristics. The active agent comprises more than 50% by weight of the formulation so that the smallest effective dose may be achieved. Although the mechanism is not fully known, it is thought that during application and while on the host, either or both the carrier components and the active agent of the formulation facilitates distribution of the agent over the surface of the animal and to the parasite. The carrier may also facilitate migration of the pyrethroid component to cover relatively all of the animal body surface for effective ectoparasite control. In the optimal composition, the carrier may also comprise ingredients that soothe or prevent irritation as well as merely employing solvents that are non-irritating.
The choice of carrier can also be varied to optimize frequency of dosing according to particular environmental conditions. For example, oily carriers resist washing. Formulations comprised of oily carriers reduce dosing frequency for hosts exposed to rain and water. Formulations comprised of aqueous carriers are more suited to dry environs. If the host is in dry environs the aqueous formulation is less likely to be washed off and the required frequency of dosing remains low.
Formulations with pyrethroid concentrations in excess of 50% by weight can be packaged in a single dose package. For example, a single 1 cubic centimeter (cc) dose of a liquid formulation comprised of permethrin and 35% 2-(2-methoxy-ethoxy)ethanol can be packaged in a collapsible 1 cc tube. Because, the formulation avoids the use of strong organic solvents like xylene, cyclohexanone, and toluene, there is greater choice of tube material. Single dose containers make storage and disposal more convenient for animal owners.
Multiple dose liquid formulations can be packaged in containers, possibly photoresistant containers, of more than 1 cc capacity. The high concentration composition also decreases container size requirements for multiple dose containers as well as the container size requirements for single dose containers for larger animals. Again, the smaller container sizes are more conveniently stored and disposed.